Pliers for crimping thimbles on electric cables

ABSTRACT

The object of the invention is a pair of crimping pliers that comprises two arms ( 10 ) and ( 12 ), a fixed jaw and a movable jaw ( 34 ), which is articulated in regard to the two arms, and a hinge link interposed between the two arms. 
     This pair of pliers displays an angular point for forming an arch perpendicular to which is positioned the axis A 3.    
     The present pair of pliers also has angular values and ratios of given lengths.

FIELD OF THE INVENTION

The present invention refers to a pair of crimping pliers, particularlyfor joining terminals to electric cables.

BACKGROUND OF THE INVENTION

The ends of electric cables have to include connecting elements, such asdifferent types of terminals, in order to provide connections thatdepend on the applications.

Nevertheless, the mode of fixation always remains the same and consistsin a deformation of one part of the terminal, forming a sleeve in whicha cable is preferably inserted. This deformation action is calledcrimping.

The dimensions of the terminals vary according to the applications, butremain of necessity reduced, because the pair of pliers is operated byhand.

On the other hand, the applied force required for obtaining a goodquality crimping of terminals on the cables remains important and anarrangement of levers is provided for these pliers for multiplying themanual force applied by the operator.

Known from U.S. Pat. No. 2,814,222 is a pair of crimping pliers thatconsists of a movable jaw and a multiplying lever.

This pair of pliers is simple, but the straight upper arm supports allof the stresses generated by the pressure of the movable jaw and theaxis of rotation of the movable jaw is subjected to strong stresses. Thecrimping force is weakly multiplied.

In general, the tools of most recent prior art, particularly thosedescribed in the patent applications EP A 536,641 and EP A 536,652comprise one arm, the end of which constitutes a fixed jaw, and a secondarm, which operates, through a system of levers, a movable jaw thatrotates around a pivot point that is an integral part of the first arm;when the operator squeezes the arms, this causes the movable jaw to comeagainst the fixed jaw with a considerable squeezing force.

Any element interposed between the two jaws is subjected to themultiplied squeezing force obtained through the system of levers.

Moreover, known from U.S. Pat. No. 5,280,716 is a tool of the generaltype above, the two arms of which are joined to each other through anarticulated hinge link on, on the one hand, a fixed axis that is anintegral part of the arm bearing the fixed jaw and, on the other hand, amovable axis in an oblong opening placed in the other arm.

In a likewise known manner, the fixed jaw can be advantageouslyfurnished with a turret that bears a number of indentations with a meansof indexing this turret so that the desired indentation is maintainedwith respect to the movable jaw during the squeezing action.

Provided for in the known arrangements is a strong multiplication but asmall opening of the jaws, which is not particularly adapted to theoperator, especially when, prior to crimping, the terminals display aconsiderable diameter. On the other hand, it is appropriate to reducethe opening of the arms in order to make the manipulations morepractical.

Moreover, it is necessary to avoid having the stresses at the level ofthe pivot point greater than the forces transmitted at the level of thejaws themselves, because, in this case, the efficiency is not optimal.

These pliers are made of light metallic materials, such as aluminumalloys, so as to attain a compromise between the different factors suchas cost/quality/performance.

In order to improve these factors still further, it has been providedthat such pliers be made of composite materials, such as fiber-loaded orfiber-reinforced polymer compositions.

Nevertheless, particularly in the case of a composite materialrealization, it is necessary to pursue several objectives and, with thisaim in view, the present invention proposes a pair of crimping pliersthat makes it possible, in particular:

-   -   to reduce the stresses perpendicular to all pivot points to a        value that is less than that of the force exerted at the level        of the jaws;    -   to produce a significant opening of the jaws for a given        multiplied force, but a limited opening of the arms; and    -   to retain a significant multiplied force so as to ensure a good        quality of crimping.

SUMMARY OF THE INVENTION

To this end, the object of the present invention is a pair of crimpingpliers, particularly for terminals on electric cables, comprising anupper arm bearing a fixed jaw with at least one indentation at its end,a lower arm, a hinge link that is interposed between said upper arm andsaid lower arm and that is articulated around the axes A1, A2, a movablejaw that has an indentation and is articulated, in relation to the upperarm, around an axis A3 and, in relation to the lower arm, around an axisA4, characterized in that the distance between the axes A1 and A2 isroughly equal to the distance between the axes A3 and A4 and in that theupper arm displays an angular point defining a body of the upper arm anda head of the upper arm, with the internal angle a, directed towards thelower arm, being less than 180°.

In accordance with another characteristic feature, the displacementcircle of the axis A2 in relation to the axis A1, the displacementcircle of the axis A4 in relation to the axis A2, and the displacementcircle of the axis A4 in relation to the axis A3 have a roughlyidentical diameter.

Such a pair of pliers is particularly noteworthy in that the particulararrangement of the axes of articulation makes it possible largely toequilibrate the stresses at the level of the different axes, whileproducing a significant force at the level of the jaws and, at the sametime, having a limited opening of the jaws.

In accordance with a characteristic arrangement, the angle α is 120°.

In accordance with another characteristic feature, the axis ofarticulation, A3, of the movable jaw is positioned perpendicular to theangular point.

Moreover, the axis A1 is positioned behind the axis A2 in relation tothe jaws.

The pair of pliers is also characterized in that different angles havedefined values:

-   -   the angle β, defined by the segments [A4–A3] and [A4–M2], is        less than 90°;    -   the angle δ, defined by the segments [A1–A3] and [A1–A2], is        less than 90°; and    -   the opening angle γ of the upper arm (10) and lower arm (12) is        less than 50°.

According to a refined variant, the fixed jaw comprises a turret,provided with indentations and mounted so as to rotate around an axis,and provided with a means of indexing the position of this turret.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is now described in detail in regard to apreferred, non-limiting embodiment that is illustrated in the appendeddrawings, among which the different figures represent the following:

FIG. 1, a perspective view of a pair of crimping pliers in accordancewith the present invention, in closed position;

FIG. 2, a side view from above of this same pair of pliers;

FIG. 3, a simplified and side view from above of the pair of pliers inaccordance with the present invention, in open position;

FIG. 4, a simplified and side view from above of the pair of pliers inaccordance with the present invention, in closed position;

FIGS. 5A and 5B, views of the same pair of pliers in open and closedpositions, showing the displacements following the circles of theprinciple points of articulation.

DETAILED DESCRIPTION

The pair of pliers in accordance with the present invention, representedin FIG. 1, comprises an upper arm 10 and a lower arm 12. Each arm iscomposed of two plates or is cast so as to leave a central gap 14 and 16that permits the displacements of the different pieces.

The upper arm bears a safety catch 18 that engages between the two arms.In every case, this catch prevents contact of the arms perpendicular tothe hand grip zone. Indeed, in the event that a piece breaks or there isa handling error, it serves to prevent any accidental pinching of thefingers of the operator.

In the case of a metallic realization, the plates are riveted and therivets 20 appear in the figures.

A hinge link 22 is interposed between the arms 10 and 12. This hingelink is mounted in an articulated manner around the axis A1 in relationto the upper arm 10 and around the axis A2 in relation to the lower arm12. The axis A1 is situated behind the axis A2 in relation to the jaws.

The upper arm 10 bears a fixed jaw 24 at its end with an indentation M1.This arm displays, in addition, an angular point 26 that defines a body10-1 of the upper arm and a head 10-2 of the upper arm.

The internal angle α, directed towards the lower arm and defined by thebody 10-1 and the head 10-2 of the upper arm, is less than 180°,preferably of the order of 120°.

In the preferred embodiment represented, the head 10-2 of the upper armis equipped with a turret 28 that is mounted so as to rotate around anaxis 30. This turret comprises several indentations 32 on its peripheryand a means of indexing, which is not represented and makes it possibleto maintain one, M1, of these indentations 32 in fixed position.

This is only a refinement of the pair of pliers in accordance with theinvention; the upper arm 10 could bear, at its end, a single indentationthat is fixed and of given profile, without changing the constitutiveelements of the pair of pliers, providing a solution of the posedproblems in the same way and affording the same advantages.

A movable jaw 34 is interposed between the upper and lower arms. Thisjaw is articulated around an axis A3 in relation to the upper arm 10 andaround an axis A4 in relation to the lower arm 12. This jaw bears anindentation M2 at its end, which is intended to engage the indentationM1 when the pair of pliers is closed, as well be explained later.

The angle β, defined by the segment [A4–A3] and [A4–M2], also has agiven value, which is less than 90° C. As for the distances d[A1,A2] andd[A3,A4], they are roughly equal.

It can be seen in the arrangement presented that the axis ofarticulation, A1, is in back on the upper arm so as to increase thedistance d[A1,A3]. Moreover, this makes it possible to extend thedistance d[A1,A2] so as to make it roughly identical to the distanced[A3,A4], as was pointed out above. Thus, d[A1,A2]/d[A3,A4] is close to1.

A third angle, the opening angle γ, has to be kept at a maximum value,preferably a value less than 50°.

From FIGS. 5A and 5B, it is possible to compare the displacement circlesof the different axes.

It is seen that the principle axes of the pair of pliers in accordancewith the present invention move in relation to one another by followingcircles of roughly identical diameter. This translates into anequilibrated distribution of the stresses on each of the axes, becausethe arms of the lever required for the multiplication are of the sameorder of length.

The circle C2-1 corresponds to the displacement of the axis A2 inrelation to the axis A1.

The circle C4-2 corresponds to the displacement of the axis A4 inrelation to the axis A2.

The circle C4-3 corresponds to the displacement of the axis A4 inrelation to the axis A3.

It is also seen that moving the axis A1 toward the back, in relation tothe arrangements of prior art, makes it also possible to lengthen thedistance covered by the arc of the circle described by the axes A2 andA4 in relation to the axis A1 and A3.

The force exerted by the movable jaw on the fixed jaw is directed fromM2 toward M1 or toward the axis 30 of the turret when one is providedfor.

The axis A2 is positioned at the vertex of an arch of stress recoverydefined by the two segments [A1–A3] and [A3–(30)] or [A3–M1], dependingon the arrangement. This reinforces the strength at this point.

During all the movement of opening and especially of closing the pair ofpliers, the angle δ stays at values less than 90°.

The pair of pliers realized in this way offers a certain ergonomics,which is due largely to the reduced degree of opening of the arms aswell as to the equilibrated stresses on the different axes, whichthereby increases the longevity of this pair of pliers.

Such a pair of pliers can be made of composite materials without fearingpoints of fragility produced by very significant localized stresses.

1. A pair of crimping pliers comprising an upper arm (10) bearing afixed jaw with at least one indentation (M1) at its end, a lower arm(12), a hinge link (22) that is interposed between said upper arm andsaid lower arm and that is articulated around the axes A1 and A2, amovable jaw (34) that has an indentation (M2) cooperable with said oneindentation (M1) for crimping a workpiece and is articulated, inrelation to the upper arm, around an axis A3 and, in relation to thelower arm, around an axis A4, characterized in that the distance betweenthe axes A1 and A2 is roughly equal to the distance between the axes A3and A4 and wherein said indentation (M2) on said movable jaw isrotatable relative to said axis A3 and maintained at a fixed distancefrom said axis A3.
 2. The pair of crimping pliers in accordance withclaim 1, further characterized in that the displacement of the axis A4corresponds to a circle (C4-2) centered with respect to the axis A2. 3.The pair of crimping pliers in accordance with claim 1, furthercharacterized in that the axis A1 is positioned behind the axis A2 inrelation to the jaws.
 4. The pair of crimping pliers in accordance withclaim 1, further characterized in that the displacement circle (C2-1) ofthe axis A2 in relation to the axis A1, the displacement circle (C4-2)of the axis A4 in relation to the axis A2, and the displacement circle(C4-3) of the axis A4 in relation to the axis A3 have a roughlyidentical diameter.
 5. The pair of crimping pliers in accordance withclaim 1, further characterized in that an angle β, defined by a segmentjoining the axis A4 and A3 and by a segment joining the axis A4 and theindentation M2, is less than 90°.
 6. The pair of crimping pliers inaccordance with claim 1, further characterized in that an angle δ,defined by a segment joining the axis A1 and A3 and by a segment joiningthe axes A1 and A2 is less than 90°.
 7. The pair of crimping pliers inaccordance with claim 1, further characterized in that an opening angleγ, defined by the upper (10) and lower (12) arms, is less than 50°. 8.The pair of crimping pliers in accordance with claim 1, furthercharacterized in that the fixed jaw (24) comprises a turret (28),provided with indentations (32) and mounted so as to rotate around anaxis (30), and provided with a means of indexing the position of theturret.
 9. The pair of crimping pliers in accordance with claim 1,characterized in that it is made of composite materials.
 10. The pair ofcrimping pliers in accordance with claim 8 wherein an angle α, definedby a segment joining the axes A1 and A3 and by a segment joining theaxis A3 and the rotation axis (30) of the turret (28), is less than180°.
 11. A pair of terminal crimping pliers comprising: an upper armcomprising a fixed jaw with at least one indentation at its end; a lowerarm; a hinge link that is interposed between the upper arm and the lowerarm, wherein the hinge is articulated around a first axis on the upperarm and a second axis on the lower arm; a movable jaw that has anindentation cooperable with said one indentation for crimping aterminal, wherein the movable jaw is articulated around a third axis onthe upper arm and around a fourth axis on the lower arm wherein theindentation of the movable jaw is rotatable relative to the third axisand maintained at a fixed distance from said third axis, and wherein afirst distance between the first and second axes is substantially equalto a second distance between the third and fourth axes.
 12. The pair ofterminal crimping pliers in accordance with claim 11, furthercharacterized in that a displacement of the fourth axis corresponds to acircle centered with respect to the second axis.
 13. The pair ofterminal crimping pliers in accordance with claim 11, furthercharacterized in that the first axis is positioned behind the secondaxis in relation to the jaws.
 14. The pair of terminal crimping pliersin accordance with claim 11, further characterized in that a firstdisplacement circle of the second axis in relation to the first axis, asecond displacement circle of the fourth axis in relation to the secondaxis, and a third displacement circle of the fourth axis in relation tothe third axis have substantially a same diameter.
 15. The pair ofterminal crimping pliers in accordance with claim 11, furthercharacterized in that an angle β, defined by a segment joining thefourth axis and the third axis and by a segment joining the fourth axisand the indentation, is less than 90°.
 16. The pair of terminal crimpingpliers in accordance with claim 11, further characterized in that anangle δ, defined by a segment joining the first axis and the third axisand by a segment joining the first axes and the second axis, is lessthan 90°.
 17. The pair of terminal crimping pliers in accordance withclaim 11, further characterized in that an opening angle γ, defined bythe upper and lower arms, is less than 50°.
 18. The pair of terminalcrimping pliers in accordance with claim 11, further characterized inthat the fixed jaw comprises a turret provided with indentations andmounted so as to rotate around an fifth axis, and provided with anindexing system for indexing positioning of the turret relative to theupper arm.
 19. The pair of terminal crimping pliers in accordance withclaim 18 wherein an angle α, defined by a segment joining the first andsecond axes and by a segment joining the third axis and the fifth axisof the turret, is less than 180°.